The Wheel is broadly been divided into four realms: 1. Hub, 2. Inner circle (divided into two parts), 3. Body of the Wheel (divided by six spokes), and 4. Rim. All are in the grips of Wrathful Yama, as depicted in the painting.
The hub depicts three spiritual poisons in the form of three animals a pig, symbolizes delusions (moha), a snake symbolizes aversion, hatred (dvesha), and a cock, passion (raga). The hub is surrounded by an inner circle, which is divided into two parts. The left side from bottom upwards depicts Adepts who have done good deeds and consequently ascended to the world of gods, while the right side, from top to bottom depicts beings that have indulged in evil deeds and consequently descended into hell. The body of the wheel, which is divided into six parts, surrounds the inner circle. The existence in the first three worlds is considered superior or good, and the last three inferior or bad. And these world are shown in this relation in the picture, the highest being heaven, and the lowest hell.
The first and the upper one region of the Wheel is heaven in which the palaces of gods have been shown. A lute Buddha is standing in this region to help the gods. According to tradition gods who born from lotus bosoms enjoy heavenly delights. They are subject to law of anityata, of birth, life, death and rebirth. They may live for millions of years in heaven, but when their merits are exhausted they have to come down. Heaven is followed by the world of asuras (titans). This world is depicted below on the right of heaven. The titans were expelled from heaven because of their pride. They fight the gods for the fruits of the wish giving tree whose roots are in their realms but fruits are in the world of gods. The third one is the realm of humans, below the left of heaven. In this region generally suffering of human life is depicted. The fourth on is the animals, depicted below the world of asuras. The animals (tiryag-yoni), live in a fearful world of uncontrolled instincts. The fifth position is the realm of tantalized ghosts, shown below the world of humans. Animal faced and emaciated ghosts, as shown in the present painting, whose insatiable greed in past births have given them tantalizing thirst and hunger. The lowest realm is the hell (naraka), presided by Yamaraja, the king and judge of the dead. This realm is divided into two parts cold and hot. The cold hell is shown on the right of this realm, and the hot hell on the left. Standing Buddha is depicted in all realms to help the beings.
The outermost circle (rim of the Wheel) is made up of twelve segments, illustrating the twelve nidanas or interdependent causes of rebirth, the scheme that the Buddha offered through which to understand the biological process of life and death it begins from ignorance, which is misknowledge about the states of the egocentric self, and ends with old age and death. The unchallenged force of ignorance again leads to another life and another and another endless suffering.
This description by Dr. Shailendra Kumar Verma, Ph.D. His doctorate thesis being on the "Emergence and Evolution of the Buddha Image (From its inception to 8th century A.D)."